VETERINARSKI ARHIV 69 (5), 251-260, 1999

ISSN 1331-8055 Published in Croatia

Disposition kinetics, renal clearance and urinary
excretion of kanamycin in goats

Asma Nafeesa¹, Ataka Rashid¹, Tahira Iqbal¹, Munir A. Sheikh¹, and Muhammad Nawaz²*

¹Department of Chemistry, University of Agriculture, Faisalabad, Pakistan

²Department of Physiology and Pharmacology,
University of Agriculture, Faisalabad, Pakistan

* Contact address:
Prof. Dr. Muhammad Nawaz,
Department of Physiology & Pharmacology, University of Agriculture, Faisalabad 38040, Pakistan,
Phone: 92 41 624 607; Fax: 92 41 624 607; E-mail: nawazn@paknet4.ptc.pk

Nafeesa, A., A. Rashid, T. Iqbal, M. A. Sheikh, M. Nawaz: Disposition kinetics, renal clearance and urinary excretion of kanamycin in goats. Vet. arhiv 69, 251-260, 1999.

ABSTRACT

The disposition kinetics, renal clearance and urinary excretion of kanamycin were investigated in eight female goats following intravenous injection of a single dose 5 mg/kg body mass. Based on Cp=Ae^-at+Be^-ßt, elimination half life of the drug was 2.87±0.12 hours, volume of distribution (Vd_(area)) 0.58±0.03 l/kg and total body clearance was 2.39±0.19 ml/min kg. The renal clearance of endogenous creatinine was 1.28±0.40 ml/min kg and kanamycin was 0.33±0.14 ml/min kg being about one fourth of the filtration clearance. Renal clearance was 13.8% of the total body clearance. The renal excretory mechanisms involved glomerular filtration, excreting only 10.3% of the intravenous dose of kanamycin through urine.

Key words: kanamycin, disposition kinetics, renal clearance, urinary excretion, goat

Introduction

Precise dosage regimen of chemotherapeutic agents is based on disposition kinetics studies carried out preferably in the target species and environments. Such studies are mostly conducted in countries from where the drugs are exported to countries where environments are different. The bio-disposition and fate of various drugs have been found to differ in diverse geographical locations (Nawaz et al., 1988). Environmental influences on glomerular filtration rate, blood composition, blood and urine pH in domestic ruminants significantly influenced the disposition and fate of drugs and were described by the original term "geonetics"; the geographical influences on genetics (Nawaz, 1994). Geonetical influences create an awareness of the need for studying bio-disposition and fate of drugs in target species and environments. Kanamycin is a commonly used antibiotic in veterinary medicine. Therefore, its disposition kinetics, renal clearance and urinary excretion of kanamycin were investigated in goats.

Materials and methods

The disposition kinetics, renal clearance and urinary excretion of kanamycin were investigated in goats.

Animals

The experiments were performed on 8 healthy female Beetle breed goats belonging to the Livestock Production & Research Institute, Bahadarnagar, Okara. The mean ±SE value for body mass of the goats was 49±2 kg. All animals were kept under uniform management conditions. The animals were sent out for grazing in the mornings until mid-day and then kept in pens for rest of the day, where they were fed green fodder of the season. The goats had free access to water. During the experiments, animals were not given food and water for about 8 hours.

Drug administration

Kanamycin (Kanachron^(r) injection Star Labs Ltd., Pakistan) was injected through the right jugular vein at a dosage rate of 5 mg/kg body mass.

Sampling

For collection of blood samples, an intravenous cannula was placed in the left jugular vein. Control blood samples were drawn in all experiments prior to drug administration. Blood samples were taken at 5, 10, 15 and 30 minutes and then at 1, 1.5, 2, 3, 4, 5 and 6 hours after drug administration. Blood samples drawn beyond 6 hours showed no detectable drug concentrations. Blood was collected in heparinized centrifuge tubes, plasma was separated and stored in the freezer (-20 °C) until analysis.

For quantitative collection of the urine samples, a balloon catheter (Rush No. 14, 30 ml) was aseptically inserted into the urinary bladder through the urethra. The open end of the catheter was attached to a collection reservoir to ensure quantitative urine collection. Renal clearance studies were performed on the same goats. At 30 min after drug administration the urinary bladder was emptied completely and washed with distilled water through the catheter. After washing, the first urine sample was collected at 30 min, with more samples collected at 60, 120, 240 minutes after drug administration. The volume of each urine sample was measured. For clearance experiments, blood samples were drawn in the middle of each urine collection period.

For the study of urinary excretion, the urine voided until 4, 6, 8, 10 and 12 hours after drug administration were collected. The urinary excretion of kanamycin was expressed as the percentage mean ±SE of the dose.

Analysis

The pH values of urine samples were recorded by means of pH meter (Labsco) with a glass electrode at 37 °C. Concentration of kanamycin in plasma and urine samples was determined by microbiological assay according to the Disk agar diffusion method described by ARRET et al. (1971) using Bacillus subtilis as test organism. Concentration of endogenous creatinine in the plasma and urine samples was determined by Jaffe reaction described by BONSNES and TAUSSKY (1945).

Calculations

Disposition kinetics (two-compartment model) parameters were calculated with the computer program MWPHARM version 3.02 a Mediware product Holland. This program calculates the regression coefficient of best fit to depict the compartmental analysis for pharmacokinetics parameters. Other calculations and graphs were made using Microsoft Excel 97 software for PC. The renal clearance of endogenous creatinine was used for the estimation of glomerular filtration rate (GFR). Renal clearance was calculated by the formulas given by SWENSON (1985):

Cl_ren=U_c×U_v/P_c

Where Cl_ren is renal clearance, U_c and P_c are concentration of the substance in urine and plasma, and U_v is rate of urine flow. Influence of urine pH, rate of urine flow and plasma drug concentration on the renal clearance of drug was examined by regression/correlation analysis. The statistical calculations were carried out according to the standard method, and results have been presented as mean ±SE.

Results

Disposition kinetics

The mean ±SE values for the plasma concentration of kanamycin on a semi-logarithmic scale against time have been shown for the eight goats in Fig 1. A bi-exponential decline in kanamycin plasma concentration against time implied two-compartment open model for disposition kinetic analysis. The level of drug in blood declined rapidly, and the concentration of kanamycin in plasma at 6 hours after injection was only 2.01±0.13 µg/ml respectively.

Fig 1. Mean ±SE plasma kanamycin concentration versus time following a single intravenous injection of 5 mg/kg body mass to 8 goats

The mean ±SE values for the disposition kinetics parameters that describe distribution and elimination of kanamycin in the 8 normal goats are given in Table 1. The distribution half time was only 8.01±0.89 minutes and elimination half-life was 2.87±0.12 hours. The apparent volume of distribution (Vd) relates drug concentration in plasma to the total amount of drug in the body after distribution equilibrium has been attained. The value of Vd_(area) was 0.58±0.03 l/kg. The total body clearance of kanamycin in goats was 2.39±0.19 ml/min kg.

Table 1. Pharmacokinetic parameters of kanamycin following intravenous injection of 5 mg/kg in 8 goats

C^op=Zero time plasma concentration, A in a and B in b phase, a & b are slopes of distribution and elimination phases. t_1/2a and t_1/2b are distribution and elimination half-life values. K₁₂ and K₂₁ are rate constants for transfer between compartment 1 and 2. Kel is rate constant for elimination, Vc is volume of central compartment, Vd_(area) is volume of distribution by area method and TBC is total body clearance.

Renal clearance

The mean +SE values for the body mass, pH of blood and urine, plasma concentration and renal clearance of endogenous creatinine and kanamycin in goats after an intravenous dose (5 mg/kg) are shown in Table 2. The mean value for the renal clearance of endogenous creatinine expressing glomerular filtration rate was 1.28±0.40 ml/min kg. The renal clearance of kanamycin was 0.33±0.14 ml/min kg or 20±8 ml/h kg. The ratio between clearance of kanamycin and endogenous creatinine was 0.26. There was no correlation between the rate of urine flow, urine pH and the plasma concentration of kanamycin with the renal clearance of kanamycin.

Table 2. Mean +SE values for the plasma concentration and renal clearance of endogenous creatinine and kanamycin in 8 goats (N=32)

Urinary excretion

The cumulative percentage of intravenous dose of kanamycin excreted in the urine of goats is presented in Fig 2. Until 12 hours after the drug administration, only 10.3±1.23% of the dose was excreted through urine.

Fig 2. Mean ±SE cumulative percentage of dose excreted in the urine of 8 goats at various time intervals following a single intravenous injection of kanamycin 5 mg/kg body mass

Discussion

Disposition kinetics

The disposition kinetics of kanamycin was described by biexponential equation that showed its goodness to fit over data similar to dog, sheep and horses (Baggot, 1977), sheep, goats, rabbits, chickens and pigeons (Lashev et al., 1992). The disposition curve revealed a rapid distribution phase t_1/2a mean ±SE 8.10±0.89 minutes similar to 4.09 minutes in dogs, 5.39 minutes in sheep and 5.42 minutes in horse (Baggot, 1977). The half-life (mean ±SE) value of kanamycin was 2.87±0.12 hours. This value is lower than 6.26 hours in buffaloes (Saeed,1994) and 6.58 hours in cows (Ghaffar et al. 1996 ). For man, half-life value 2.00 hours (Kirby et al., 1976) and 1.55 hours (Yamasku et al.,1986) has been reported. In different species of animals, half-life of kanamycin after intravenous administration was reported as 0.73 hour in dogs, 1.65 hours in sheep and 1.40 hours in horse (Baggot, 1977). Half life of kanamycin after i/m administration in horse was 1.80±0.24 hours (Baggot et al., 1981) and in milk goats was 2.16 hours (Jianyuan et al., 1989). Kanamycin is mainly eliminated from the body through urinary excretion. Longer half-life of kanamycin in goats may be related to the lower GFR in local goats (Akhtar et al., 1997) while shorter half-life in dog and humans being may due to acidic urine pH in these species.

The apparent volume of distribution (Vd) 0.58±0.03 l/kg was higher than 217 ml/kg in sheep, 225 ml/kg in dog, 174 ml/kg in horse (Baggot, 1977) and human volunteers 209 ml/kg (Yamasku et al., 1986). It was lower than 1.32±0.18 l/kg in buffaloes (Saeed,1994) and 1.28±0.18 l/kg in cows (Ghaffar et al., 1996). The difference in apparent volume of distribution may be due to different extent of plasma protein binding of kanamycin in different species. The apparent volume of distribution lower than one indicates that the concentration of kanamycin in tissues is lower than in plasma, and it is thought that the drug is mainly restricted to the central compartment. The lower kanamycin concentrations in tissue extravascular fluids are probably less advantageous than in blood in determining the outcome of therapy in injection localised in tissues other than blood.

Total body clearance mean ±SE 2.39±0.19 ml/min kg was not much different from the values in dog, sheep and horse 3.51, 1.52 and 1.43 ml/min kg, respectively (Baggot, 1977), 3.21±0.72 ml/min kg in beagles (Baggot, 1978), 1.56 ml/min kg in man (Yamasku et al., 1986), 2.5 ml/min kg in cows (Ghaffar et al., 1996) and similar to 2.38±0.17 ml/min kg in buffaloes (Saeed, 1994). The pH of blood was 7.35±0.036, being within the range of pH reported earlier for the ruminant species (Nawaz and Shah, 1984). In goats, earlier studies during the winter season showed higher values of blood pH 7.75 (Nawaz et al., 1990) and 7.81 (Iqbal et al., 1986). The lowest value of blood pH was recorded in goats (7.33) during summer and the highest value was in cows (8.03) during winter seasons (Nawaz et al., 1988). The mean value for urine pH 7.99±0.22 was similar to the previously determined value of urine pH 7.90 in goats during summer (Javed et al., 1984). The values of diuresis mean ±SE 0.08±0.02 ml/min kg was similar to the values 0.052 and 0.085 ml/min kg reported by Javed et al., 1984 and Nawaz et al., 1990, respectively. A lower value of 0.021 ml/min kg was reported by Shah et al. (1983).

The renal clearance of creatinine in goats showed mean ±SE 1.28±0.40 ml/min kg, comparable to the previously reported value 1.43±0.21 ml/min kg (Akhtar et al., 1997). The mean ±SE value of renal clearance of kanamycin was 0.33±0.14 ml/min kg in goats. Lower values of the kanamycin renal clearance than the GFR indicate that the excretion of the drug through kidneys involves glomerular filtration and extensive renal tubular back diffusion or reabsorption. Previous studies have shown that in man, the renal clearance of kanamycin was less than the filtration or creatinine clearance 83 vs 120 ml/min (Kirby et al., 1976). Total body clearance of kanamycin was 2.39±0.19 ml/min kg against renal clearance of 0.33±0.14 ml/min kg, indicating that the kidneys contribute only 13.8% of the total body clearance.

Urinary excretion

At 12 hours after kanamycin administration, 10.3±1.2% of total dose was excreted in urine, being lower than the dose excreted in human volunteers 74 - 94% after 8 hours (Yamasku et al., 1986), renal clearance of kanamycin being only 13.8% of the total body clearance. These studies indicate that more than 85% of the drug was eliminated through routes other than the urinary routes.

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Received: 4 March 1999
Accepted: 20 October 1999

Nafeesa, A., A. Rashid, T. Iqbal, M. A. Sheikh, M. Nawaz: Kinetika odlaganja, procišcavanje putem bubrega i izlucivanje kanamicina mokracom u koza. Vet. arhiv 69, 251-260, 1999.

SAZETAK

Istrazivani su kinetika odlaganja, procišcavanje putem bubrega i izlucivanje kanamicina mokracom u osam koza zenskog spola, a nakon intravenske injekcije jednokratne doze od 5 mg/kg tjelesne mase. Na osnovi Cp = Ae^-at+Be^-bt, poluvrijeme elimanacije lijeka bilo je 2,87 ±0,12 sati, volumen distribucije (Vd_(area)) 0,58±0,03 l/kg, a ukupno tjelesno procišcavanje 2,39±0,19 ml/min kg. Bubrezno procišcavanje endogenog kreatinina bilo je 1,28±0,40 ml/min kg, a kanamicina 0,33±0,14 ml/min kg što predstavlja oko cetvrtine procišcavanja filtracijom. Procišcavanje putem bubrega predstavljalo je 13,8% ukupnog tjelesnog procišcavanja. Bubrezni ekskretorni mehanizmi ukljucivali su glomerularnu filtraciju putem koje je izlucivano mokracom samo 10,3% intravenske doze kanamicina.

Kljucne rijeci: kanamicin, dispozicije odlaganja, bubrezno procišcavanje, bubrezni klirens, urinarna ekskrecija, izlucivanje mokracom, koza